Influence of resin cross-linking on solid-phase chemistry.

A range of PS-DVB resins were prepared by suspension polymerization with styrene, p-chloromethyl styrene, and DVB. Yields of polymerization increased (from 40% to almost 80%) with increasing cross-linking. The beads exhibited the expected swelling characteristics, with the 0.3% resin swelling to almost 9 times its dry volume in CHCl3. Kinetics of cleavage of the dye Methyl Red from the range of Rink linked resins showed rate enhancements of up to 500% between the 6.0 and the 0.3% cross-linked resins. Total synthesis of Kawaguchipeptin B was carried out on the resins, and their performance during the syntheses was investigated. Contrary to expectations, the purities of the cyclic peptide product increased with increasing resin cross-linking doubling from the 0.3-6.0% resin. A Suzuki reaction showed the half-lives of reaction increased with increasing resin cross-linking with an 11-fold increase in half-life between the 0.3-2.7% resin. Surprisingly, we observed very little reaction in the case of the 3.0 and 6.0% cross-linked resins.